The process of producing 3-hydroxypropionic acid (3-HP) involves fermenting sugar(s) at or near neutral pH. Keeping the fermentation at or near neutral pH, however, leads to formation of a salt of 3-HP, most commonly an (alkyl)ammonium 3-hydroxypropionate. Examples of such salts of 3-HP include ammonium 3-hydroxypropionate (A3HP), along with those having a mono-, di-, or tri-alkyl ammonium cation, for example a methyl-, a dimethyl-, or a trimethyl ammonium cation. In order to arrive at the 3-HP, the A3HP salt from the fermentation process needs to be “split” into ammonia and 3-HP. Once split, the ammonia is recycled and the 3-HP is converted to a more useful product, e.g. acrylic acid.
There are, however, problems in “splitting” the A3HP salt into ammonia and 3-HP. For example, in one approach to “splitting” the A3HP salt an aqueous solution of A3HP is heated at either atmospheric or reduced pressure in a process called “thermal salt-splitting” (TSS). TSS removes water from the aqueous solution, which is undesirable for two reasons: 1) the viscosity of the resulting solution increases to the point where it is very difficult to handle, and 2) the resulting 3-HP product can undergo condensation reactions both with itself (to form, e.g., oligomeric esters) and with other acids and amines present in the mixture, such as acetic and glutamic acids. These condensation reactions complicate both the subsequent dehydration reaction and the separation processes. Reactions with amines to form amides are especially undesirable as it is difficult to convert these products to acrylic acid.
There is a need, therefor, in the art for a salt-splitting liquid and a process that uses the salt-splitting liquid to “split” the A3HP salt into ammonia and 3-HP that minimizes any increase in the viscosity and the condensation reactions of the 3-HP. There is a need, therefor, in the art for a process that minimizes any increase in the viscosity and the condensation reactions of the 3-HP.